GB-B-1533059 discloses the use of a pre-sulphided absorbent comprising copper sulphide for the absorption of mercury from a natural gas stream containing mercury. The pre-sulphided absorbent is prepared by forming a precursor comprising basic copper carbonate and a refractory cement binder, and then contacting the precursor with a gaseous stream containing a sulphur compound, e.g. hydrogen sulphide, so as to fully sulphide the copper compound. The pre-sulphided absorbent is then used to remove mercury from a natural gas stream. It is also shown that an absorbent comprising copper in the reduced, i.e. metallic, state is less effective at absorbing mercury than the pre-sulphided absorbent.
EP 0480603 describes a process for the removal of mercury from a stream wherein an absorbent comprising a metal sulphide is prepared in situ, preferably by the stream also containing a sulphur compound thereby concomitantly preparing the mercury absorbent and absorbing the mercury, such that the formation of ineffective and undesired metal compounds e.g. sulphates is avoided.
Such materials, especially those described in GB-1533059, undergo considerable physiochemical changes upon treatment with sulphur compounds to form the metal sulphide phases known to be effective for mercury removal. The physiochemical changes result in reduced crush strength and an increased susceptibility to attrition, particularly with high metal sulphide containing materials. It is therefore desirable to increase the crush strength whilst maintaining attrition resistance. We have found that a combination of binders and support material in the absorbent overcomes the problems associated with prior art materials.